An AC pulse arc welding method is a method of carrying out welding by supplying a wire to a base material at a set wire feed rate, and alternately supplying a straight polarity current and a reversed polarity pulse current between the wire and the base material. Herein, the straight polarity current is a current that is allowed to flow so as to form globules at a tip of the wire by melting the wire during a straight polarity period in which the wire is in negative polarity. The reversed polarity pulse current is a current that is allowed to flow so as to transfer the globules at the tip of the wire to the base material by supplying a pulse current during a reversed polarity period in which the wire is in positive polarity. An example of known AC pulse arc welding method includes a method of setting a peak current energizing period and a peak current value in a reversed polarity period according to the conditions of a wire and a shield gas, and the like, in order to stabilize the arc. Another example is a method of uniformly setting an AC frequency and a straight polarity current value according to a wire feed rate (see, for example, Patent Document 1).
In a conventional AC pulse arc welding method, a straight polarity current value and a straight polarity period are uniformly determined according to a wire feed rate. Therefore, the energizing ratio in the reversed polarity period and the straight polarity period cannot be changed arbitrarily, so that it is not possible to make use of a merit of consumable electrode type AC pulse welding capable of controlling the welding penetration depth.
Furthermore, in order to cope with such problems, a welding apparatus capable of individually setting a polarity ratio, parameters such as a current in the reversed polarity period, and parameters such as a current in the straight polarity period may be possible. However, when the polarity ratio is changed in such a welding apparatus, in order to carry out appropriate welding, it is necessary to individually adjust parameters other than the polarity ratio. Thus, it takes a long time to find appropriate welding conditions.    [Patent Document 1] Japanese Patent Unexamined Publication No. H1-186279